src/common/align.h

   1 /*
   2  * Copyright (C) 2010-2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
   3  *
   4  * SPDX-License-Identifier: MIT
   5  *
   6  */
   7
   8 #ifndef _LTTNG_ALIGN_H
   9 #define _LTTNG_ALIGN_H
  10
  11 #include "bug.h"
  12 #include <unistd.h>
  13 #include <limits.h>
  14
  15 #ifndef PAGE_SIZE       /* Cygwin limits.h defines its own PAGE_SIZE. */
  16 #define PAGE_SIZE               sysconf(_SC_PAGE_SIZE)
  17 #endif
  18
  19 #ifndef PAGE_MASK       /* macOS defines its own PAGE_MASK. */
  20 #define PAGE_MASK               (~(PAGE_SIZE - 1))
  21 #endif
  22
  23 #define __ALIGN_MASK(v, mask)   (((v) + (mask)) & ~(mask))
  24
  25 #ifndef ALIGN           /* macOS defines its own ALIGN. */
  26 #define ALIGN(v, align)         __ALIGN_MASK(v, (__typeof__(v)) (align) - 1)
  27 #endif
  28
  29 #define __ALIGN_FLOOR_MASK(v, mask)     ((v) & ~(mask))
  30
  31 #ifndef ALIGN_FLOOR
  32 #define ALIGN_FLOOR(v, align)   __ALIGN_FLOOR_MASK(v, (__typeof__(v)) (align) - 1)
  33 #endif
  34
  35 #define PAGE_ALIGN(addr)        ALIGN(addr, PAGE_SIZE)
  36
  37 /**
  38  * offset_align - Calculate the offset needed to align an object on its natural
  39  *                alignment towards higher addresses.
  40  * @align_drift:  object offset from an "alignment"-aligned address.
  41  * @alignment:    natural object alignment. Must be non-zero, power of 2.
  42  *
  43  * Returns the offset that must be added to align towards higher
  44  * addresses.
  45  */
  46 #define offset_align(align_drift, alignment)                                   \
  47         ({                                                                     \
  48                 LTTNG_BUILD_RUNTIME_BUG_ON((alignment) == 0                    \
  49                                    || ((alignment) & ((alignment) - 1)));      \
  50                 (((alignment) - (align_drift)) & ((alignment) - 1));           \
  51         })
  52
  53 /**
  54  * offset_align_floor - Calculate the offset needed to align an object
  55  *                      on its natural alignment towards lower addresses.
  56  * @align_drift:  object offset from an "alignment"-aligned address.
  57  * @alignment:    natural object alignment. Must be non-zero, power of 2.
  58  *
  59  * Returns the offset that must be substracted to align towards lower addresses.
  60  */
  61 #define offset_align_floor(align_drift, alignment)                             \
  62         ({                                                                     \
  63                 LTTNG_BUILD_RUNTIME_BUG_ON((alignment) == 0                    \
  64                                    || ((alignment) & ((alignment) - 1)));      \
  65                 (((align_drift) - (alignment)) & ((alignment) - 1));           \
  66         })
  67
  68 #endif /* _LTTNG_ALIGN_H */